HDP fill with reduced void formation and spacer damage

ABSTRACT

A method for filling gaps between structures includes forming a plurality of high aspect ratio structures adjacent to one another with gaps, forming a first dielectric layer on tops of the structures and conformally depositing a spacer dielectric layer over the structures. The spacer dielectric layer is removed from horizontal surfaces and a protection layer is conformally deposited over the structures. The gaps are filled with a flowable dielectric, which is recessed to a height along sidewalls of the structures by a selective etch process such that the protection layer protects the spacer dielectric layer on sidewalls of the structures. The first dielectric layer and the spacer dielectric layer are exposed above the height using a higher etch resistance than the protection layer to maintain dimensions of the spacer layer dielectric through the etching processes. The gaps are filled by a high density plasma fill.

BACKGROUND Technical Field

The present invention relates to semiconductor devices and processingmethods, and more particularly to improved dielectric fill processesespecially with components with small gaps between them.

Description of the Related Art

Semiconductor devices include a wide range of topographical features. Insome devices, high aspect ratio features cause deep and narrow gaps toform between them. The gaps are often filled with a dielectric fillprocess. The dielectric fill process often fills the gaps from thebottom up. As material is deposited in the bottom of the gap, materialbegins to form on sidewalls of the features as well. This can causepinch off and result in voids.

Scaling a pitch of features (e.g., making device sizes smaller) can leadto issues during the fill process and during process steps that recessthe fill material to expose more of the features. In one example, thefeatures may include gate structures with dielectric spacers and hardmask caps. During a fill process or a recess process, voids can form andhard mask or spacer damage can occur. This may result in issues withthese structures later on in the process or with the reliability of thedevice after manufacture.

SUMMARY

A method for filling gaps between structures in a semiconductor deviceincludes forming a plurality of high aspect ratio structures adjacent toone another to provide gaps therebetween; forming a first dielectriclayer on top of the high aspect ratio structures; conformally depositinga spacer dielectric layer over the high aspect ratio structures;removing the spacer dielectric layer from horizontal surfaces;conformally depositing a protection layer over the high aspect ratiostructures; filling the gaps with a flowable dielectric; recessing theflowable dielectric to a height along sidewalls of the high aspect ratiostructures by a selective etch process such that the protection layerprotects the spacer dielectric layer on sidewalls of the high aspectratio structures; exposing the first dielectric layer and the spacerdielectric layer by an etch process that selectively removes theprotection layer above the height wherein the first dielectric layer andthe spacer dielectric layer have a higher etch resistance than theprotection layer to maintain dimensions of the spacer layer dielectricthrough the recessing step and the exposing step; and filling the gapsby a high density plasma fill.

Another method for filling gaps between structures in a semiconductordevice includes patterning a stack of layers including at least a gatematerial, a first dielectric layer and a hard mask layer to form aplurality of high aspect ratio structures adjacent to one another toprovide gaps therebetween; conformally depositing a spacer dielectriclayer over the high aspect ratio structures; removing the spacerdielectric layer from horizontal surfaces to form spacers on sidewallsof the high aspect ratio structures; forming source and drain regionsadjacent to the spacers; conformally depositing a protection layer overthe high aspect ratio structures and the source and drain regions;

filling the gaps with a flowable dielectric; recessing the flowabledielectric to a height along the sidewalls of the high aspect ratiostructures by a selective etch process such that the protection layerprotects the spacers of the high aspect ratio structures; exposing thefirst dielectric layer and the spacers by an etch process thatselectively removes the hard mask and the protection layer above theheight wherein the first dielectric layer and the spacer dielectriclayer have a higher etch resistance than the hard mask and theprotection layer to maintain a thickness of the spacers through therecessing step and the exposing step; and filling the gaps by a highdensity plasma fill.

A semiconductor device includes a plurality of high aspect ratio gatestructures formed adjacent to one another and forming gaps therebetween,the high aspect ratio gate structures including a top surface. Spacersare formed on sidewalls of the high aspect ratio gate structures, thespacers having a higher etch resistance than SiN in a selective oxideetch to maintain dimensions of the spacers during etch processes. Thegaps are filled with a protection layer formed on the spacers to aheight on the spacers, a flowable dielectric formed to below the heightwithin the protection layer and a high density plasma dielectric fillabove the height. Contacts are formed through the high density plasmadielectric fill, the flowable dielectric and the protection layer toconnect to source and drain regions.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 is a cross-sectional view showing high aspect ratio structureswith a thin dielectric layer having a different etch selectivity than ahard mask layer on top of the thin dielectric layer in accordance withthe present principles;

FIG. 2 is a cross-sectional view of FIG. 1 showing a sidewall spacerlayer formed of a same material as the thin dielectric layer and theformation of epitaxially grown structures adjacent to sidewall spacerson the high aspect ratio structures in accordance with the presentprinciples;

FIG. 3 is a cross-sectional view of FIG. 2 showing a protection layerformed over the high aspect ratio structures in accordance with thepresent principles;

FIG. 4 is a cross-sectional view of FIG. 3 showing a flowable dielectricfill between the high aspect ratio structures in accordance with thepresent principles;

FIG. 5 is a cross-sectional view of FIG. 4 showing the flowabledielectric fill recessed selectively to the protection layer down to aheight between the high aspect ratio structures in accordance with thepresent principles;

FIG. 6 is a cross-sectional view of FIG. 5 showing a portion of theprotection layer and the hard mask layer removed in accordance with thepresent principles;

FIG. 7 is a cross-sectional view of FIG. 6 showing an HDP fill inaccordance with the present principles;

FIG. 8 is a cross-sectional view of FIG. 7 showing the gate structureafter a cap reactive ion etch for replacement gate embodiments, a dummygate is removed, high-k dielectric and gate metal are deposited within agate region in accordance with the present principles;

FIG. 9 is a cross-sectional view of FIG. 8 showing contacts holes etchedinto the interlayer dielectric layers and stopping on the protectionlayer in accordance with the present principles;

FIG. 10 is a cross-sectional view of FIG. 9 showing removal of theprotective liner, deposition of a contact liner and metal contactsformed in accordance with the present principles; and

FIG. 11 is a block/flow diagram showing a method for filling gapsbetween structures in a semiconductor device in accordance withillustrative embodiments.

DETAILED DESCRIPTION

In accordance with the present principles, device and methods forfabricating devices are provided that reduce the formation of voids anddamage to adjacent structures during a gap fill process and/or a gapfill recess process. In one embodiment, a liner etch process isperformed selective to spacers on high aspect ratio structures after aflowable dielectric fill and recess process. The liner protects thespacers on high aspect ratio structures during the fill and recess stepsbut then provides a selective removal to provide valuable “real-estate”when continuing to fill gaps. This process serves to prevent voidformation and spacer damage. In one particularly useful embodiment, asemiconductor device includes a plurality of gate structures havingspacers formed on sidewalls thereof. The spacers may include, e.g.,SiBCN spacers. A SiN liner etch process selective to the SiBCN spacers,after a flowable oxide recess, may be employed to provide a larger gapwhen continuing to oxide fill to prevent void formation and spacerdamage.

It is to be understood that the present invention will be described interms of a given illustrative architecture; however, otherarchitectures, structures, substrate materials and process features andsteps may be varied within the scope of the present invention.

It will also be understood that when an element such as a layer, regionor substrate is referred to as being “on” or “over” another element, itcan be directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

A design for an integrated circuit chip may be created in a graphicalcomputer programming language, and stored in a computer storage medium(such as a disk, tape, physical hard drive, or virtual hard drive suchas in a storage access network). If the designer does not fabricatechips or the photolithographic masks used to fabricate chips, thedesigner may transmit the resulting design by physical means (e.g., byproviding a copy of the storage medium storing the design) orelectronically (e.g., through the Internet) to such entities, directlyor indirectly. The stored design is then converted into the appropriateformat (e.g., GDSII) for the fabrication of photolithographic masks,which typically include multiple copies of the chip design in questionthat are to be formed on a wafer. The photolithographic masks areutilized to define areas of the wafer (and/or the layers thereon) to beetched or otherwise processed.

Methods as described herein may be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present principles, as well as other variations thereof, means thata particular feature, structure, characteristic, and so forth describedin connection with the embodiment is included in at least one embodimentof the present principles. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This may be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, a cross-sectional view isshown for a partially fabricated semiconductor device 10 in accordancewith one embodiment. Device 10 includes substrate 16. The substrate 16is appropriately doped to form wells for the respective devices or isotherwise processed depending on the devices to be fabricated. Thesubstrate 16 may include a Si substrate, although other materials, maybe employed, e.g., SiGe, SiC, etc. A gate layer 14 may includepolysilicon as a dummy structure or a conductor as a gate firststructure. It should be understood that the present principles may beemployed for dummy gate structures; this process includes accommodationslater in the processing for replacing the dummy gate with a conductor.

A thin dielectric layer 18 is formed over the gate layer 14, and a caplayer or hard mask layer 20 is formed on the thin dielectric layer 18.In one embodiment, thin dielectric layer 18 includes a nitride, and moreparticularly, SiBCN. The cap layer 20 may include a nitride as well. Thenitride may include SiN and may be formed using a plasma enhancedchemical vapor deposition (PECVD) process. The cap layer 20 should beselectively removable with respect to the thin dielectric layer 18. Thethin dielectric layer 18 may include a thickness of between about 5 nmto about 15 nm. A mask dielectric layer 22 may include an oxide, and isformed over the cap layer 20.

The mask dielectric layer 22, the cap layer 20, thin dielectric layer 18and the gate layer 14 are patterned to form high aspect ratio structures24 down to the substrate 16 with gaps 25 therebetween. Etch processes,such as reactive ion etch processes, are employed using the maskdielectric layer 22 as a mask, which may be patterned using alithographic process. The etch chemistries may be altered depending onthe material being etched although a single etch chemistry and processmay be employed, e.g., an oxygen plasma, etc. It should be understoodthat the high aspect ratio structures (e.g., height to width ratio ofgreater than 1:1 and more preferably greater than 3:1) described hereare illustrative and that other components or features may be employedin accordance with the present principles.

Referring to FIG. 2, a spacer dielectric 26 is conformally depositedover the device 10. The spacer dielectric 26 preferably includes a samematerial (same etch characteristics) as the thin dielectric layer 18.The spacer dielectric 26 may include a nitride and, in particular, aSiBCN. A reactive ion etch (RIE) or other process is performed to removethe spacer dielectric 26 from horizontal surfaces. The spacer dielectric26 may include a thickness, after etching of between about 4 nm to about8 nm on vertical surfaces, but can exceed, e.g., 10-12 nm. The spacerdielectric 26 thickness depends on spacer quality, dielectric constant,damage during recess and/or high density plasma (HDP) fill, etc. Recessetch removal of the spacer depends on which process is employed, e.g.,selective etching may only remove 1-2 nm.

The substrate 16 may be recessed or at least cleaned to prepare thesurfaces for the formation of source/drain (S/D) regions 28. S/D regions28 are epitaxially grown from the substrate 16. An epitaxial growthprocess is employed to grow a monocrystalline structure for devices suchas field effect transistors. The S/D regions 28 may be grown over thesubstrate 16 and may be formed adjacent to the spacer dielectric 26 onopposite sides of the structures 24. The S/D regions 28 may include thesame material as the substrate 16 or may include a material having asimilar or same lattice structure as the substrate 16. The S/D regions28 may be doped in-situ or may be doped by implantation, diffusion orother process after their formation.

Referring to FIG. 3, a protection layer 30 is deposited over the device10 to protect the structures 24. The protection layer 30 may include athin layer, e.g., about 3 nm, of SiN or other dielectric material. Theprotection layer 30 may be scaled up or down in thickness depending onself-aligned contact RIE selectivity, gate pitch and specified contactsize. The protection layer 30 protects the structures 24 from futureprocessing as will be described.

Referring to FIG. 4, a flowable dielectric 32 is formed over theprotection layer 30. The flowable dielectric 32 may include a flowableoxide material. The flowable dielectric 32 fills in gaps betweenstructures 24. The device 10 is then subjected to a planarizing processsuch as a chemical mechanical polish (CMP). The flowable dielectric 32will be recessed as will be described.

Referring to FIG. 5, the flowable dielectric 32 is recessed to a height34 using an etch process that is highly selective in removing theflowable dielectric relative to the protection layer 30. In oneembodiment, the protection layer 30, the spacer dielectric 26 and thecap layer 20 (if present) or the thin dielectric layer 18 (if the caplayer is removed) may all include a form of nitride. Therefore, a highlyselective process for the removal oxide against nitride may be provided.Other material combinations may also be employed. During the recess, theprotection layer 30 preserves the underlying spacer dielectric 26 sothat there is no loss of the spacer dielectric 22 as a result of therecessing process. In conventional process flows, the spacer dielectricbegins to be eroded as a result of the recess process.

Referring to FIG. 6, an etch process is performed to remove theprotection layer 30 in exposed areas (e.g., above the height 34). Theprotection layer 30 is preferably removed selectively to the spacerdielectric 26 and the cap layer 20 (if present is removed relative tothe thin dielectric layer 18). In one embodiment, the protection layer30 and the cap layer include SiN and the thin dielectric layer 18 andthe spacer dielectric 26 include SiBCN. In this way, the SiN can beselectively removed relative to the SiBCN. Other material combinationsmay be employed having the selectivity relationships as describedherein.

FIG. 6 shows a fabricated state ready for a high density plasma (HDP)fill. The structure provided in accordance with the present principles,provides horns 36 or additional dielectric material at the top cornersof the structures 24. In addition, the spacer dielectric 26 and the thindielectric layer 18 remains substantially intact through the recessprocess. Further, using a higher selectivity material for the spacers(26) counteracts etching losses, which permits the use of a thinnerspacer dielectric layer 26. This results in additional space for the HDPfill and provides a significant decrease in the formation of voidsbetween the structures 24. The gap size between high aspect ratiostructures will, in effect, be increased without altering a pitchbetween the high aspect ratio structures. In one example, using, e.g.,SiBCN permits higher selectivity than SiN. In one embodiment, for a 44nm node technology, openings 38 for a HDP fill significantly enlargefrom, e.g., about 8 nm to about 14 nm (an increase of approximately75%). The structures 24 remain on pitch but more space is availablebetween them to perform the HDP fill.

In addition, the present principles provide a more controllable process.There is no top profile sharpening or nitride coverage loss fromsidewalls of the structure 24. The thin dielectric 18 and the spacerdielectric layer 26 encapsulate and protect the structures 24. Whenfilling the gaps by a high density plasma fill, formation of voids isprevented by providing the gap size that has been increased. The spacerdielectric layer 26 is formed to exceed a height of the thin dielectriclayer 18 on sidewalls of the high aspect ratio structures 24 to formhorns 36 on top corners of the high aspect ratio structures 24 prior tofilling the gaps by the high density plasma fill.

Conventional processes thin the sidewall spacers and especially the topcorners on the structures, giving the structures (e.g., gates or dummygates) the appearance of a picket in cross-section since the dielectricis thinned by etching. The horns 36 and material selection assist inpreventing this in accordance with the present embodiments.

Referring to FIG. 7, the process can continue with an HDP oxidedeposition process to provide an HDP fill and cap 40. The HDP fill 40has a significantly reduced likelihood of forming voids betweenstructures 24 in accordance with the present principles. A CMP processmay be performed to take a top surface of the HDP fill 40 down to layer18, which acts as an etch stop layer (FIG. 8).

Referring of FIG. 8, if a dummy gate structure is employed, layer 18 isremoved and dummy gate structures 14 and dummy dielectric (in contactwith the substrate 16) are removed. The layer 18 (e.g., SiBCN) and thegate layer 14 may be removed using a RIE. The gate layer 14 may be adummy gate which can be pulled in a replacement gate process. If theprocess includes a gate first design, then FIG. 8 can be skipped as anactive gate is already formed. A replacement metal gate (RMG) includesthe formation of a high-k dielectric (e.g., HfO₂) 52 and a work functionmetal and metal fill (e.g., Tungsten) 54, which are deposited andplanarized. The protection layer 30 and the dielectric layer 32 remainthroughout the gate replacement process.

Referring to FIG. 9, contact holes 56 are opened down to the protectionlayer 30. The contact holes 56 are self-aligned and etched using an RIEprocess. The RIE stops on protection layer 30 to prevent the epitaxiallyformed S/D regions 28 from being damaged or etched.

Referring to FIG. 10, the protection layer 30 is selectively etched toexpose the surface of the S/D regions 28. The etch chemistry is changedto remove the protection layer in a separate etch process. Aself-aligned contact liner 58 is deposited and metallization isdeposited to form contacts 60. The contact liner may include TiN, TaN,etc., and the contacts may include W or other metals. Fabrication of thedevice 10 can continue in accordance with the device design. This mayinclude the formation of metallizations and other structures as areknown in the art.

In some embodiments, portions of the protection layer 30 (on thesidewalls adjacent to spacers 26) may remain in place to provideadditional protection to the sidewall spacers 26. It should beunderstood that while the present description illustratively describedthe structures 24 as gate structures, the present principles should notbe construed as being limited by these structures and that any highaspect ratio structures may benefit in accordance with the presentprinciples.

Referring to FIG. 11, a method for filling gaps between structures in asemiconductor device is illustratively shown in accordance with thepresent principles. In some alternative implementations, the functionsnoted in the blocks may occur out of the order noted in the figures. Forexample, two blocks shown in succession may, in fact, be executedsubstantially concurrently, or the blocks may sometimes be executed inthe reverse order, depending upon the functionality involved. It willalso be noted that each block of the block diagrams and/or flowchartillustration, and combinations of blocks in the block diagrams and/orflowchart illustration, can be implemented by special purposehardware-based systems that perform the specified functions or acts orcarry out combinations of special purpose hardware and computerinstructions.

In block 102, a stack of layers is patterned to form high aspect ratiostructures. The stack may include at least a gate material (e.g., adummy gate or gate conductor), a first dielectric layer (a thindielectric layer) and a hard mask layer to form a plurality of highaspect ratio structures adjacent to one another with gaps therebetween.Other layers may also be included to assist in the formation of the highaspect ratio structures. In one embodiment, the first dielectric layerincludes a material with a higher etch resistance than SiN, e.g., SiBCN.

In block 104, a spacer dielectric layer is conformally deposited overthe high aspect ratio structures. The spacer dielectric layer mayinclude a thickness of about 12 nm or less. Using a thin spacer a gapsize between high aspect ratio structures is increased without alteringa pitch between the high aspect ratio structures. The spacer dielectriclayer may include a material having a higher etch resistance than SiN,e.g., SiBCN.

In block 105, the spacer dielectric layer is deposited over the highaspect ratio structures to exceed a height of the first dielectric layeron sidewalls of the high aspect ratio structures to form horns on topcorners of the high aspect ratio structures to protect the structuresbefore and during the filling of the gaps by the high density plasmafill.

In block 106, the spacer dielectric layer is removed from horizontalsurfaces to form spacers on sidewalls of the high aspect ratiostructures. In block 108, source and drain regions are formed adjacentto the spacers. This step may be optional depending on the devices beingformed. In block 110, a protection layer is conformally deposited overthe high aspect ratio structures and the source and drain regions, ifpresent. In block 112, the gaps are filled with a flowable dielectric.This may include a CMP process to planarize a top surface. In block 114,the flowable dielectric is recessed to a height along the sidewalls ofthe high aspect ratio structures by a selective etch process such thatthe protection layer protects the spacers of the high aspect ratiostructures. In block 116, the first dielectric layer and the spacers areexposed by an etch process that selectively removes the hard mask andthe protection layer above the height wherein the first dielectric layerand the spacer dielectric layer have a higher etch resistance than thehard mask and the protection layer to maintain a thickness of thespacers through the recessing step (block 114) and the exposing step(block 116).

In block 118, the gaps are filled by a high density plasma fill. Thisincludes avoiding formation of voids by providing an increased gap sizeusing thinner spacers with a higher etch resistance (and bolstered byetch protection throughout the process and a permanent protectionlayer). The protection layer and the flowable dielectric layer remainbetween the gate structures and provide protection for the spacers forcontact hole etching. In block 120, contact holes are formed through theHDP fill and the flowable dielectric and stop on the protection layerusing a self-aligned RIE process. The RIE process selectively removesoxide relative to the gate conductor and spacer materials. The flowabledielectric protects the spacers, and the protection layer protects theunderlying source and drain regions. In block 122, the protection layeris then removed in a different etch process to open up and expose thesource and drain regions. In block 124, a contact liner is formed. Inblock 126, contacts are deposited and processing continues.

Having described preferred embodiments for devices and methods for HDPfill with reduced void formation (which are intended to be illustrativeand not limiting), it is noted that modifications and variations can bemade by persons skilled in the art in light of the above teachings. Itis therefore to be understood that changes may be made in the particularembodiment disclosed which are within the scope of the invention asoutlined by the appended claims. Having thus described aspects of theinvention, with the details and particularity required by the patentlaws, what is claimed and desired protected by Letters Patent is setforth in the appended claims.

The invention claimed is:
 1. A method for method filling gaps betweenstructures in a semiconductor device, comprising: forming a plurality ofhigh aspect ratio structures adjacent to one another to provide gapstherebetween; forming a spacer dielectric layer over the high aspectstructures; forming spacers on sidewalls of the high aspect ratiostructures by removing the spacer dielectric layer from horizontalsurfaces; conformally depositing a protection layer over the high aspectratio structures; filling the gaps with a flowable dielectric; recessingthe flowable dielectric to a height along the sidewalls of the highaspect ratio structures such that the protection layer protects thespacer dielectric layer on the sidewalls of the high aspect ratiostructures; and selectively removing the protection layer above theheight to maintain dimensions of the spacer layer dielectric.
 2. Themethod as recited in claim 1, wherein forming the plurality of highaspect ratio structures includes patterning a stack of layers includingat least a gate material and a first dielectric layer.
 3. The method asrecited in claim 2, wherein the stack of layers further includes a hardmask layer over the first dielectric layer.
 4. The method as recited inclaim 3, wherein selectively removing the protection layer includesselectively removing the hard mask layer and the protection layer abovethe height to maintain dimensions of the spacer layer dielectric.
 5. Themethod as recited in claim 4, wherein selectively removing the hard masklayer and the protection layer includes forming horns on top corners ofeach of the plurality of high aspect ratio structures.
 6. The method asrecited in claim 5, wherein the horns include dielectric material at thetop corners of each of the plurality of high aspect ratio structures. 7.The method as recited in claim 2, wherein the first dielectric layerincludes a material having a higher etch resistance than SiN.
 8. Themethod as recited in claim 7, wherein the first dielectric layerincludes SiBCN.
 9. The method as recited in claim 1, wherein selectivelyremoving the protection layer includes exposing the spacer dielectriclayer by an etch process.
 10. The method as recited in claim 1, whereinthe spacer dielectric layer has a higher etch resistance than theprotection layer.
 11. The method as recited in claim 1, furthercomprising filling the gaps by a high density plasma fill.
 12. Themethod as recited in claim 11, wherein filling the gaps by the highdensity plasma fill includes avoiding formation of voids by providing agap size between the high aspect ratio structures.
 13. The method asrecited in claim 1, wherein forming the spacer dielectric layer over thehigh aspect ratio structures includes conformally depositing the spacerdielectric layer with a material having a higher etch resistance thanSiN.
 14. The method as recited in claim 1, wherein forming the spacerdielectric layer over the high aspect ratio structures includesconformally depositing the spacer dielectric layer with a thickness of12 nm or less to increase a gap size between the high aspect ratiostructures without altering a pitch between the high aspect ratiostructures.
 15. The method as recited in claim 1, wherein forming thespacer dielectric layer includes conformally depositing the spacerdielectric layer along the sidewalls of the high aspect ratiostructures.
 16. The method as recited in claim 1, further comprisingforming contact holes by etching through the flowable dielectric and theprotection layer.
 17. The method as recited in claim 1, whereinconformally depositing the protection layer includes conformallydepositing the protection layer in the gaps.
 18. The method as recitedin claim 1, wherein selectively removing the protection layer includesforming horns on top corners of each of the plurality of high aspectratio structures.
 19. The method as recited in claim 18, wherein thehorns include dielectric material at the top corners of each of theplurality of high aspect ratio structures.
 20. The method as recited inclaim 3, wherein the hard mask layer is formed using a plasma enhancedchemical vapor deposition process.